Tracking and Tires and Pressures
09-29-16, 12:13 PM
#32
Found some videos of the latest event.
That bump in the first clip knocked my alignment off. Toe'd the right rear out by 0.26 degrees resulting in excessive oversteer turning left. Ended up having my 1st exploratory run being the fastest of the day, and afternoon runs 1-2 seconds slower when it was warmer and grippier. Was top 10 in PAX in the AM, and the slower runs eventually dropping me down to 16th out of 95 cars. Another decent showing for the RC-F despite the problems. Might actually invest in RE71Rs next year to see what the car is really capable of. Surprised that little jump there was able to mess up the alignment.
That bump in the first clip knocked my alignment off. Toe'd the right rear out by 0.26 degrees resulting in excessive oversteer turning left. Ended up having my 1st exploratory run being the fastest of the day, and afternoon runs 1-2 seconds slower when it was warmer and grippier. Was top 10 in PAX in the AM, and the slower runs eventually dropping me down to 16th out of 95 cars. Another decent showing for the RC-F despite the problems. Might actually invest in RE71Rs next year to see what the car is really capable of. Surprised that little jump there was able to mess up the alignment.
09-29-16, 01:55 PM
#33
Lead Lap
09-29-17, 05:58 PM
#34
No understeer at 1G. Still very neutral. I can push more and go a little faster before it starts to understeer. Keep in mind this is 1 single corner. The rollover will overheat that area of the tire much more, it's not something that can be sustained. Take a few corners like this, and it'll overheat, get greasy, and start understeering at that point. The spacers helped a little, I wasn't able to get this level of grip even for a single corner before the spacers.
I don't think anyone makes camber plates or anything for the front yet. I've only been able to find rear camber arms, but that's pointless until the front is fixed.
I don't think anyone makes camber plates or anything for the front yet. I've only been able to find rear camber arms, but that's pointless until the front is fixed.
09-29-17, 06:32 PM
#36
It’s detailed above. 20mm front, none in the rear. 0 toe up front, 0.01 toe rear. No camber adjustments available. Stock ride height. if you lower the car, you’ll magically dial in front negative camber, I would say it’s required if you want any track action. The bonus to these toe settings is that it greatly extends tire life.
I’ve also tweaked the tire pressures a bit when I went on a long road trip this summer. If you’re not driving hard, the OEM pressures is better suited which makes the car less darty.
I’ve also tweaked the tire pressures a bit when I went on a long road trip this summer. If you’re not driving hard, the OEM pressures is better suited which makes the car less darty.
09-29-17, 07:30 PM
#37
It’s detailed above. 20mm front, none in the rear. 0 toe up front, 0.01 toe rear. No camber adjustments available. Stock ride height. if you lower the car, you’ll magically dial in front negative camber, I would say it’s required if you want any track action. The bonus to these toe settings is that it greatly extends tire life.
I’ve also tweaked the tire pressures a bit when I went on a long road trip this summer. If you’re not driving hard, the OEM pressures is better suited which makes the car less darty.
I’ve also tweaked the tire pressures a bit when I went on a long road trip this summer. If you’re not driving hard, the OEM pressures is better suited which makes the car less darty.
im shocked at how aggressive the front spacer is but I would have guessed that negative csmber would happen as a result of going wider. Any reason you didnt then add like 10mm in the rear for similar affect?
Was considering a 15mm all around. Or
swift spring drop with a 10mm all around and then dial in alignment from there.
09-29-17, 07:49 PM
#38
thank you. I honestly got lost up above in the detsils so I appreciate you sharing
im shocked at how aggressive the front spacer is but I would have guessed that negative csmber would happen as a result of going wider. Any reason you didnt then add like 10mm in the rear for similar affect?
Was considering a 15mm all around. Or
swift spring drop with a 10mm all around and then dial in alignment from there.
im shocked at how aggressive the front spacer is but I would have guessed that negative csmber would happen as a result of going wider. Any reason you didnt then add like 10mm in the rear for similar affect?
Was considering a 15mm all around. Or
swift spring drop with a 10mm all around and then dial in alignment from there.
I didn’t space the rears because it didn’t need more grip. Improving rear grip would have unbalanced the car from my liking, tougher to rotate on throttle near the limit.
Also wanted to add after 2 years, I still don’t see anyone making camber plates for the front suspension still. Disappointing.
Last edited by rage2; 09-29-17 at 07:53 PM.
10-03-17, 09:36 PM
#39
Lexus Test Driver
Yes there is a slight negative camber effect with spacers up front. Nothing to write home about. You want real negative camber so you dont kill the front tires at the track, you’ll need to lower your car.
I didn’t space the rears because it didn’t need more grip. Improving rear grip would have unbalanced the car from my liking, tougher to rotate on throttle near the limit.
Also wanted to add after 2 years, I still don’t see anyone making camber plates for the front suspension still. Disappointing.
I didn’t space the rears because it didn’t need more grip. Improving rear grip would have unbalanced the car from my liking, tougher to rotate on throttle near the limit.
Also wanted to add after 2 years, I still don’t see anyone making camber plates for the front suspension still. Disappointing.
can you elaborate? I can see more grip as the stance is wider, but camber should be same??
T-demand makes upper arms for our car that allow camber adjustment.
My fronts set at -2.7 currently.
Lowering the car to 26" will make the front camber statically sit at approx at -1.2 without any manipulation.
The rears lowered to 26" will be at approx -1.5
Fyi.
Btw I was told our suspension are double arm design so it's not possible to adjust camber with just a plate like Hondas. We would need either a shorter upper arm or longer lower arm to gain negative camber.
Last edited by Mingofish; 10-03-17 at 09:44 PM.
10-07-17, 03:44 AM
#40
Curious, do you have RR-racing Ultimate Steering Response System? That should clean up a few things in the handling area.
10-07-17, 08:09 PM
#41
Tech Info Resource
iTrader: (2)
There is no camber adjustment on the IS F, RC F, or GS F. Specs are published in TIS, but your Lexus dealer may not have updated the software for the alignment rack (completely unrelated to Lexus) so the RC F doesn't show up.
Dealers are idiots about alignment. Hennessey Lexus of Gwinnett supposedly aligned my IS F after significant work was done at the body shop. Their numbers showed they failed to calibrate the rack before they used it. I took it to NTB immediately, and all numbers were dead on the money.
If the camber is not balanced in the front, the subframe needs to move left or right to accomplish this. It will also correct caster issues.
Put camber plates on this car. Yep, changing the angle of the shocks without moving the upper and lower control arms won't change a single number in the alignment. Lexus does not make F cars of any kind with McPherson struts, so anything you learned from cars that have them does not apply.
My cold pressure for track days on my IS F is 32 psi. They get to 44 psi right quick after a few laps. Note 44 psi is the maximum pressure on the tire's sidewall, which means it will support the greatest load at that pressure without having a failure. Might want to think about that before you set your tire pressures.
Spacers do not change camber in any way. They change scrub radius (usually making it worse), and every suspension dimension the factory sweated over to make the car handle predictably. If you do not own the software to determine what happens to roll centers, instant centers, roll axis, scrub radius, roll couple, and a host of other important suspension parameters, you are guessing at best, and very likely make the car perform worse. You might like how it feels, but feeling good and being fast are not the same thing.
I tuned mini-sprint chassis for a bit. Learned a whole lot. Also learned arbitrarily lowering a production car very often results in slower lap times. There are myriad reasons for this, but it is really rare to be able to lower a car and make it measurably perform better without a whole lot of other changes.
Dealers are idiots about alignment. Hennessey Lexus of Gwinnett supposedly aligned my IS F after significant work was done at the body shop. Their numbers showed they failed to calibrate the rack before they used it. I took it to NTB immediately, and all numbers were dead on the money.
If the camber is not balanced in the front, the subframe needs to move left or right to accomplish this. It will also correct caster issues.
Put camber plates on this car. Yep, changing the angle of the shocks without moving the upper and lower control arms won't change a single number in the alignment. Lexus does not make F cars of any kind with McPherson struts, so anything you learned from cars that have them does not apply.
My cold pressure for track days on my IS F is 32 psi. They get to 44 psi right quick after a few laps. Note 44 psi is the maximum pressure on the tire's sidewall, which means it will support the greatest load at that pressure without having a failure. Might want to think about that before you set your tire pressures.
Spacers do not change camber in any way. They change scrub radius (usually making it worse), and every suspension dimension the factory sweated over to make the car handle predictably. If you do not own the software to determine what happens to roll centers, instant centers, roll axis, scrub radius, roll couple, and a host of other important suspension parameters, you are guessing at best, and very likely make the car perform worse. You might like how it feels, but feeling good and being fast are not the same thing.
I tuned mini-sprint chassis for a bit. Learned a whole lot. Also learned arbitrarily lowering a production car very often results in slower lap times. There are myriad reasons for this, but it is really rare to be able to lower a car and make it measurably perform better without a whole lot of other changes.
The following 2 users liked this post by lobuxracer:
konichiwa3 (10-08-17),
Mingofish (10-09-17)
10-08-17, 07:29 PM
#42
There is no camber adjustment on the IS F, RC F, or GS F. Specs are published in TIS, but your Lexus dealer may not have updated the software for the alignment rack (completely unrelated to Lexus) so the RC F doesn't show up.
Dealers are idiots about alignment. Hennessey Lexus of Gwinnett supposedly aligned my IS F after significant work was done at the body shop. Their numbers showed they failed to calibrate the rack before they used it. I took it to NTB immediately, and all numbers were dead on the money.
If the camber is not balanced in the front, the subframe needs to move left or right to accomplish this. It will also correct caster issues.
Put camber plates on this car. Yep, changing the angle of the shocks without moving the upper and lower control arms won't change a single number in the alignment. Lexus does not make F cars of any kind with McPherson struts, so anything you learned from cars that have them does not apply.
My cold pressure for track days on my IS F is 32 psi. They get to 44 psi right quick after a few laps. Note 44 psi is the maximum pressure on the tire's sidewall, which means it will support the greatest load at that pressure without having a failure. Might want to think about that before you set your tire pressures.
Spacers do not change camber in any way. They change scrub radius (usually making it worse), and every suspension dimension the factory sweated over to make the car handle predictably. If you do not own the software to determine what happens to roll centers, instant centers, roll axis, scrub radius, roll couple, and a host of other important suspension parameters, you are guessing at best, and very likely make the car perform worse. You might like how it feels, but feeling good and being fast are not the same thing.
I tuned mini-sprint chassis for a bit. Learned a whole lot. Also learned arbitrarily lowering a production car very often results in slower lap times. There are myriad reasons for this, but it is really rare to be able to lower a car and make it measurably perform better without a whole lot of other changes.
Dealers are idiots about alignment. Hennessey Lexus of Gwinnett supposedly aligned my IS F after significant work was done at the body shop. Their numbers showed they failed to calibrate the rack before they used it. I took it to NTB immediately, and all numbers were dead on the money.
If the camber is not balanced in the front, the subframe needs to move left or right to accomplish this. It will also correct caster issues.
Put camber plates on this car. Yep, changing the angle of the shocks without moving the upper and lower control arms won't change a single number in the alignment. Lexus does not make F cars of any kind with McPherson struts, so anything you learned from cars that have them does not apply.
My cold pressure for track days on my IS F is 32 psi. They get to 44 psi right quick after a few laps. Note 44 psi is the maximum pressure on the tire's sidewall, which means it will support the greatest load at that pressure without having a failure. Might want to think about that before you set your tire pressures.
Spacers do not change camber in any way. They change scrub radius (usually making it worse), and every suspension dimension the factory sweated over to make the car handle predictably. If you do not own the software to determine what happens to roll centers, instant centers, roll axis, scrub radius, roll couple, and a host of other important suspension parameters, you are guessing at best, and very likely make the car perform worse. You might like how it feels, but feeling good and being fast are not the same thing.
I tuned mini-sprint chassis for a bit. Learned a whole lot. Also learned arbitrarily lowering a production car very often results in slower lap times. There are myriad reasons for this, but it is really rare to be able to lower a car and make it measurably perform better without a whole lot of other changes.
Thanks again for an insightful post!
Last edited by konichiwa3; 10-08-17 at 07:42 PM.
10-09-17, 03:09 PM
#43
Tech Info Resource
iTrader: (2)
Excellent!! One reason I completely stay away from spacers. It messes with the car's suspension geometry, I even read somewhere how it negatively affects steering input. Am not about just looks, its all about performance. Why mess the performance when that's the reason why you bought an F car? Interesting what you said about lowering. Do you think this happens when you just substitute for lowering springs or would it also happen with a coilover setup that I would say has been properly tuned for instance the Figs engineering Ohlins road and track coilovers for RCF?
Thanks again for an insightful post!
Thanks again for an insightful post!
If you are looking for visual performance, ignore all the stuff about roll centers, instant centers, scrub radius, roll couple, etc., etc., and set up the car to look good. Just don't fool yourself into thinking you made the car any better from a mechanical performance perspective.
Again - arbitrarily making changes without understanding the purpose of the change will likely lead to reduced mechanical performance. If you truly want an education in chassis setup and preparation for competition, check this site: http://farnorthracing.com/modeling.html. There is a massive wealth of information there at no cost to you that will help better understand chassis tuning and will also help you understand why I am so negative about swaybars as a first change to a suspension system.
The following users liked this post:
Mingofish (10-09-17)
10-09-17, 08:23 PM
#45
Lexus Test Driver
My cold pressure for track days on my IS F is 32 psi. They get to 44 psi right quick after a few laps. Note 44 psi is the maximum pressure on the tire's sidewall, which means it will support the greatest load at that pressure without having a failure. Might want to think about that before you set your tire pressures.
thats a huge jump from 32 to 44! Were those super sports ?
I remember first few times out on the track with the OE super sports, I pushed a lot, which I'm sure heated up the tires like crazy. I was starting at 36 cold and were hitting 42-44 hot.
Since then I've swapped tires to yoko AD08R.
Been typically starting at 32 but they only get to 39-40 max, even this past summer during those 90 degrees track days.
I'm guessing different tread pattern/compound/side wall stiffness will heat up differently also, given the car and driver and exterior temp is consistent.
Got a buddy who uses nitrogen. His track pressure only varies 3-4 lb from cold to max hot.
Something to look into. I've never ever used Nitrogen.